The present invention generally relates to a method and apparatus for remotely controlling the operation of a circuit protection device, such as a circuit breaker. More specifically, the present invention is an apparatus externally connected to a circuit breaker that causes the contacts of the circuit breaker to open in response to a signal generated by a remotely located control circuit.
Previously, it has been known to provide a circuit breaker including a shunt trip apparatus that allows the breaker to be selectively operated to its tripped condition from a remote location. The shunt trip feature is commonly provided by adding a separate enclosure to the side of an existing molded circuit breaker. Typically, the separate enclosure contains a shunt trip element, such as a solenoid or lever system, that is coupled to the circuit breaker through a linking arrangement extending through the outer walls of the molded circuit breaker case.
Although this type of shunt trip apparatus allows the circuit breaker to be remotely operated, the shunt trip apparatus requires modification to the standard circuit breaker housing and the inclusion of additional operating components, such as a separate set of contacts and/or operating devices such as a solenoid. Examples of this type of shunt trip circuit breaker are illustrated in U.S. Pat. Nos. 6,034,581; 5,301,083; and 4,804,862.
In addition to the shunt trip type of remotely actuated circuit breakers, U.S. Pat. No. 4,616,206 teaches a circuit breaker having a remotely located switch that draws current through the tripping mechanism within the circuit breaker. The supply of current down through the tripping mechanism moves an SME element in the breaker, thereby allowing the breaker to move to its tripped position. However, the mechanism illustrated in the ""206 patent requires a special connection to the internal components of the circuit breaker and draws current through a portion of the breaker that does not receive current during normal circumstances.
Therefore, a need exists for an apparatus that can remotely trip a circuit breaker without requiring separate mechanical or electromechanical components to be incorporated into the operating components of the circuit breaker. Further, a need exists for an apparatus that is located remotely from the circuit breaker and does not have any physical connections to the breaker. Additionally, a need exists for an apparatus that allows the circuit breaker to operate in a normal fashion while being able to quickly move the contacts to an open position.
The present invention is a method and apparatus for remotely activating a circuit protection device, such as a circuit breaker, to cause the circuit protection device to open and create an open circuit between a power source and a load. More specifically, the present invention is a control circuit that can be connected to the load side of a circuit breaker and operated to cause a surge of current to flow through the circuit breaker to open the contacts of the circuit breaker upon command.
The control circuit of the present invention includes an impedance limiter and a switching device connected in series with each other across the power supply. The impedance limiter includes one end connected to the load side of the circuit breaker and another end coupled to the switching device. Preferably, the impedance limiter is a resistor having a selected resistance such that when the resistor is connected between the circuit breaker and ground, the impedance limiter draws a supply of current from the power source sufficient to cause the contacts of the circuit breaker to move to an open position.
The switching device of the present invention includes an internal switch that allows the switching device to move between an open position and a closed position. When the switching device is in the open position, an open circuit is present between the impedance limiter and ground. When the switching device is moved to a closed position, the impedance limiter is connected to ground potential through the switching device. Thus, when the switching device is closed, the impedance limiter draws current from the power source through the circuit breaker.
The switching device and the impedance limiter of the present invention are located externally from the circuit breaker and can be connected to any type of circuit breaker currently available. Further, the external connection between the impedance limiter and the circuit breaker does not require any internal connections to the operating components within the circuit breaker.
The switching device of the present invention receives an operating signal from a switching circuit. The switching circuit can be configured to generate an operating signal upon detecting a desired parameter. For example, the switching circuit can generate the operating signal if the voltage of the power source exceeds an over voltage reference value or falls below an under voltage reference value.